This project will collect EEG frequency and evoked potential (EP) amplitude and latency data from all of the subjects at each collection interval. EEG data will be obtained from all standard 10-20 system recording sites except Fz and Cz. The EEG spectrum (from 3-20 Hz) will be broken into the usual frequency bands and compared between groups (0, 0.5, 1, 2, and 3) as well as across time within individuals. The EP will be elicited by checkerboard shift as recorded from 01 and 02 referenced to vertex. It will be marked for peaks N1, N2, P3 and N3. The EEG and EP variables will be correlated in later stages of the project with data from other projects to uncover underlying relationships.